Piezoelectric crystal holder



Jan. 8,1946. A, PERK N Em .,z,392,69o

PIEZO-ELECTRIC CRYSTAL HOLDER Filed Sept. 28, 1943 INI/eA/T R B na ed, 4M+W Patented Jan. 8, 1946 v 2,392,690 PIEZOELECTRIGCRYSTAL HOLDER Alan James Perkins, London, and Walter George Roberts, Hove, England, assignors to Simmonds Aerocessories Limited, London, England Application September 28, 1943, Serial No. 504,17 In Great Britain October 1, 1942 2 Claims. (c1.r11 s2'1) This invention relates to piezo-electric crystal holders or mountings.

In the production of piezo-electric crystal holdem, whether of the simple air-gap, pressur air-' gap or pressure type, it is often necessary to process the crystal and then to test it in association with its electrodes in the holder in which it is to be mounted finally. As this processing and testing may have to be repeated several times, it is important that the performance of the mounted crystal shall be consistent. It is also important that when th crystal has been adjusted finally to have a, desired performance itcan be mounted in its holder and the holder permanently sealed without alteration to the periormance oi the crystal.

It is the principal object of this invention to provide a piezo-electric crystal holder which is adapted to maintain the electrical characteristics of the crystal substantially constant.

A further object of the invention is to provide a holder which is oi. robust construction and wherein the crystal and its electrodes are securely held against relativ movement.

A still further object of the invention is to provide a mounting for a piezo-electric crystal such that the electrical parameters of the crystal may be readily adjusted before the outer casing or cover is fitted and are not aflected during the fitting of such outer casing or cover.

Other objects and advantages 01' the invention will become apparent during the course of the following description of the drawing in which Fig. 1 is a perspective view of the improved crystal holder with the cover thereof removed to show the construction more clearly,

Fig. 2 is a perspective view of a part of the holder Fig. 3 is a plan view of a part of the holder, and

Fig. 4 is a central vertical section th'rough'a complete holder.

In the improved piezo-electric crystal holder in accordance with the present invention the crystal and its associated electrodes are housed within a shallow tray member of insulating material and the said tray member is a close sliding fit in an outer casing or cover,

Referring to the drawing the improved holder comprises generally a tray member I0 within which the crystal and its associated electrodes blocks i2 secured in position by the threaded ends of contact pins l3 which extend through apertures in the outer end wall or the tray l0 and are screwed into the said blocks. An insulating block it, preferably integral with the tray member I0, extends between the metal blocks l2, and the insulating block N forms with the side walls and inner end wall of the tray member ID a square crystal and electrode holding chamber. Located in the bottom of the said chamber is a thin metal contact plate l5 which has an arm i6 extending beneath one of the metal blocks l2 whereby electrical connection is made between the lower electrode I1 and one of the contact pins it. The crystal 2! and upper and lower crystal electrodes l8 and H, are a close fit in the said chamber and the crystal is clamped between th electrodes l1 and I8 by a concave spring strip I8 which bears against the upper electrode l8 at its centre portion, one end of the strip being secured by a set screw 20 within a recess in the inner end wall of the tray member I0 and the other end of the strip being screwed or otherwise secured to the insulating block it at the outer end of the tray. The set screw 20 allows the pressure exerted by the spring to be readily adjusted. The said spring, at its outer end, is formed with an arm 2| which is screwed or otherwise attached to the other metal block I! whereby electrical connection is made between the upper electrode l8 and the other contact pin it.

The crystal, its electrodes and the clamping spring are housed entirely within th confines of the tray member and it will be appreciated that, since the crystal and its electrodes are a close fit in the crystal chamber of the tray member and are clamped together by the spring, movement of the crystal and its lectrodes relatively to the tray member is efiectively restrained and there is little or no danger oi! the electrical parameters of the crystal being altered by shocks or other violent movements. As shown in Figs. 1 and 4 a reducing frame 25, shown in Fig. 2, may be readily fitted within the tray i0, whereby it can be adapted to house crystals and electrodes of smaller size. I

The outer casing or cover ll comprises a rectangular box-like member of suitable insulating material and open at on end whereby the tray member can be slid thereinto. The

tray member is a close fit in the casing so that the tray member and the outer casing support and strengthen one another. The tray member ill may be removably secured to the casing II by screws 2|, see Fig. 4,pessing through the end walloi the casing,andthe traymembermay be quickly secured within or removed rrom its casing without ai'lecting the electrical parameters of the crystal.

To allow the tray member II to be readily and eflectively sealed within the outer casing II, the tray member II is advantageously formed near its outer end with a peripheral flang 12, the the outer casing being recessed as at 23 at its open end to provide a ledge 20 against which flange 22 abuts and iorms a groove 2 for receiving suitable sealing material. 7

We claim:

1. A piezo-electric crystal holder comprising an open ended cover member, a tray mimber fitting in said cover member, said tray member having a bottom, and side and end walls, one of said walls being dimensioned to engage and close the open end of said cover member when said tray member is inserted in said cover member, said tray member being dimensioned to receive there- 'in with a close fit a crystal and its associated electrodes, means retaining said crystal and electrodes in intimate contact within said tray member, a

.bers.

ALAN JAMIE wsurm GIORBI mum's. 

